1. Field of the Invention
The present invention relates generally to a wireless communication system, and more particularly, to a method and apparatus for determining channel quality in a multi-cell wireless communication system.
2. Description of the Related Art
In general, a terminal, e.g., a Mobile Station (MS) or a User Equipment (UE), estimates a DownLink (DL) channel quality using a reference signal or a pilot signal, and reports information about the estimated channel quality (hereinafter referred to as “channel quality information”) to a Base Station (BS), a Node B (NB), or an evolved Node B (eNB), over an UpLink (UL) channel.
The BS uses received channel quality information, as criteria for allocating resources to the terminal, and for determining a Modulation & Coding Selection (MCS) level for the resource-allocated terminal.
The channel quality is determined mainly based on the Received Signal Strength (RSS) from a serving cell and an Interference Signal Strength (ISS) from an interfering cell(s). In particular, the ISS may vary significantly depending on whether the interfering cell uses resources. In addition, the interference reflected in the channel quality measured by the terminal may differ from the interference determined depending on whether the interfering cell uses resources at the time the channel quality is reflected. Therefore, the MCS level is often determined, based on whether the interfering cell uses resources at the current time.
Conventionally, however, the terminal merely reports the channel quality to the BS periodically or aperiodically, and does not report whether the interfering cell used resources at the time the terminal measured the channel quality. In the conventional technology, the BS may not determine the exact MCS level, which decreases the capacity of the wireless communication system. For example, when the terminal measures the channel quality at the time the interfering cell uses no resources, it reports a high-channel quality value to the BS. In response, a scheduler of the BS will assign a high MCS level to the terminal that has reported the high-channel quality value. However, when the interfering cell uses resources at the time the terminal is actually allocated resources, the terminal may fail to receive a high MCS level, and vice versa.
In contrast, when the terminal measures the channel quality at the same time the interfering cell uses resources, it may report a low-channel quality value to the BS. In response, the scheduler of the BS will assign a low MCS level to the terminal. However, when the interfering cell does not use resources at the time the terminal is actually allocated resources, the terminal may still receive only the low MCS level, thereby decreasing resource efficiency.